Process for the production of extensible paper yarn



May 22, 1962 H. s. WELSH 3,035,405

PROCESS FOR THE PRODUCTION OF EXTENSIBLE PAPER YARN Filed June 8, 1960 2 Sheets-Sheet 1 v 32 IIIIIIIIAV INVENTOR.

' HEW/T7 s. WELSH s W P 4/miww A TTOENEWG H. S. WELSH May 22, 1962 PROCESS FOR THE PRODUCTION OF EXTENSIBLE PAPER YARN Filed June 8, 1960 2 Sheets-Sheet 2 lua 0/0 I H INVENTOR. HEW/77' 5. WELSH ZKQMMW ATTOEN'YS United States Patent Office 3,h35,4h Patented May 22, 1962 3,035,405 PROCESS FOR THE PRODUCTION OF EXTENSIBLE PAPER YARN Hewitt S. Welsh, Short Hills, N.J., assignor to Clupak Inc, New York, N.Y., a corporation of Delaware Filed June 8, 1960, Ser. No. 34,659 4 Claims. (Cl. 57165) This invention relates to an extensible twisted paper product and to the process for producing the same. More particularly, this invention relates to an improved extensible twisted paper product having its maximum extensibility throughout in the axial direction of the product, and further to the process for producing such a paper product particularly from a paper which does not itself have any marked extensibility.

Twisted paper products presently are used for various applications, such as woven rug backing, knit paper sacks, and the like, where low cost is of paramount importance in selecting a material and where the strength and toughness of the paper product permits. A twisted paper prodnet at times is referred to as cord, strands or yarn depending upon its use, and they will be referred to sometimes herein generally as yam. These paper products are usually formed by cutting a narrow ribbon of paper from a web, moistening the paper ribbon to make it more plastic or formable, passing the moistened ribbon through a die which folds it in a longitudinal direction and then twisting the folded ribbon to produce the twisted paper product. The twisting of the ribbon increases its tensile strength, but does not substantially increase its toughness or ability to absorb impact.

The use of paper yarn formed in this manner as a competitive substitute for yarn of other material is limited presently by the low toughness and flexibility of the paper yarn. For example, jute yarn, while more expensive than paper yarn in many countries including the United States, is used in many applications where greater toughness is needed. The desirability of some extensibility in a twisted paper product for reasons other than the resulting increased toughness has been recognized for some time. Such extensibility would be desirable because of the short radius bends placed in yarn during weaving or knitting and the desirability of some stretch in the products produced from the yarn. As a means of obtaining some increased flexibility and toughness, the moisture content of prior twisted yarns used for some applications has not been reduced following the forming thereof. However, this "means of increasing the toughness of yarn is troublesome in that it requires special handling and it is only partially effective.

The principal factor contributing to the low toughness of prior twisted yarn is its low extensibility. Paper yarn made with conventional kraft paper having only its natural extensibility of around 4 percent would generally have an extensibility of a little less than 4 percent. Kraft papers are now available having a maximum extensibility of 8 to 9 percent in their longitudinal direction and having a comparably greater toughness. It has heretofore been proposed in Chad, U.S. 2,624,245 to form a paper strand using this improved high extensible paper and thereby obtain the improved feature of greater toughness in the yarn to make the yarn more useful and competitive for end product uses.

It has been found that a paper yarn formed in the usual manner and using the high extensible paper does not possess a comparable high extensibility. It has been found that some and perhaps the majority of the increased extensibility in the paper web is removed by the draw tension in passing the moistened strip of paper through the die and twisting operations, and it is only with extreme care that the increased extensibility is obtained in the twisted yarn. In addition to having less extensibility than the original paper, the direction of maximum extensibility, which was greatest in the longitudinal direction of the ribbon, is now a maximum in a direction angular to the longitudinal or axial direction of the yarn because the ribbon is twisted in forming the yarn. Thus, the maximum increased extensibility is not in the direction to provide its greatest benefit, and it is limited by the extensibility of commercially available papers.

I have found in the compaction of moistened paper webs that a plurality of layers of paper may be shrunk simultaneously by a force on the outer surface of the layers in a direction parallel to the surface thereto while maintaining a lateral pressure against the layers. This has led to the discovery that a twisted paper product suitably moistened can be compacted by a compressive force acting parallel to the axis of the product and only on a portion of its outer surface, and that the ribbon forming the twisted product will be shrunk throughout the axial direction of the product. Therefore, according to the present invention, a paper ribbon is moistened and passed through a die to fold the ribbon in the usual manner forming longitudinally extending parallel portions. The folded paper ribbon is twisted and the twisted yarn is then shrunk while it is still moist by applying compacting forces to the outer surface of the yarn and along a portion only of the circumference of the yarn. A compressive force applied in this manner has been found to impart a controlled amount of extensibility substantially uniform throughout the yarn with an accompanying increase in toughness and without impairing the commercial workability of the yarn. In fact, the workability of the yarn is increased. The compression while in a moist and plastic condition imparts a new configuration which can be pulled out by a considerable force when the yarn is dried. On untwisting the ribbon forming such a twisted paper product, it has been found that the extensibility has been imparted almost entirely to the paper ribbon rather than merely to telescope the twisted yarn as might be expected. Additionally, the extensibility added in this manner is on a slight bias in the longitudinally extending portions of the unfolded ribbon, but the extensibility is principally in an axial direction of the twisted yarn.

It is accordingly an object of the present invention to provide an improved twisted paper product having an increased extensibility and toughness.

Another object of the present invention is to provide an improved twisted paper product having a controlled increased extensibility and toughness principally in the axial direction of the product.

A further object of the present invention is to provide an improved process for increasing the extensibility of twisted yarn having a maximum extensibility in the axial direction of the yarn.

Other objects and advantages of the present invention will be apparent from the following description and the drawing in which:

FIGS. 1(a) and (b) are schematic diagrams of the process for producing the extensible twisted paper product according to the present invention;

FIG. 2 is an exaggerated transverse view of the twisted paper product passing through the compactor shown in FIG. 1(b);

FIG. 3 is a side view of a partially unwound extensible twisted product of the present invention; and

FIG. 4 is a tensile stretch diagram showing the toughness characteristics of twisted paper products.

Referring more particularly to FIG. 1(a), a narrow width ribbon of paper 15 is supplied preferably from a roll 16' of previously cut and wound paper. The paper ribbon 15 may be of any desired width, but preferably may be approximately /2 inch in width. The basis weight of the paper from which the ribbon is cut and the width of the ribbon 15 are a matter of choice depending upon the diameter and weight of the twisted paper product to be formed. The paper ribbon 15 may have only its natural extensibility which is in the order of 4 percent in its longitudinal direction, or it may have some increased extensibility, if desired.

The paper ribbon 15 passes over guide rolls 17, 18 and 19 which guide the paper ribbon 15 through a moistening bath 20 to moisten the paper ribbon 15 and to thereby increase its plasticity. The moistening bath 20 contains water and generally a lubricating agent which may be added to assist in passing the paper ribbon 15 through the subsequent folding operation. The moisture content of the ribbon 15 (a) upon leaving the moistening bath 20 is suitable for the subsequent forming operation and, as is well known in the forming of twisted paper cord, a range between 15 and 40 percent moisture is considered suitable for the forming operation.

The moistened paper ribbon 15(a) is led from the moistening bath 20 over guide roll 19 to a folding means 21. The purpose of the folding means 21 is to position the cut edges of the fiat paper ribbon 15(a) on the inside of the folded ribbon 15(1)) to reduce the possibility of side tears in the ribbon during the subsequent twisting operation. The folding means 21 comprises a die which forms the ribbon 15(b) as a plurality of longitudinally extending parallel portions folded onto themselves. While any number of folds may be provided, limited only by the width and thickness of the ribbon, I preferably fold the side of the strip towards the middle and then fold the strip again lengthwise along its middle to form four parallel extending longitudinal portions.

Upon leaving the folding means 21, the ribbon (15b) is twisted, and the twisted ribbon or yarn 15(0) is wound on a spool 25. The twisting of the ribbon 15 (b) may be obtained in a conventional manner such as by rotation of the spool 25 end over end while the yarn 15(0) is wound on the spool 25. The spool 25 also is oscillated during winding to obtain a uniform distribution of the yarn 15(c) on the spool 25.

The twisting of the ribbon tightly winds the longitudinal extending parallel portions of the ribbon 15(1)) into tightly Wound spirals having a common axis. Approximately four turns per lineal inch preferably are provided in the yarn 15(0) to assure that the spirally wound portions are closely joined, however, the number of turns may be varied depending on the width and thickness of the ribbon 15. This twisting increases the tensile strength of the yarn.

Referring now to FIG. 1(b), the twisted yarn 15(c), while still in the moist condition in which it was placed for the forming and twisting operations, is fed from the spool '25 over a guide roll 27 to a compactor unit 30. The compactor 30 is a mechanical device suitable for axially compacting the twisted yarn 15 (0) while simultaneously exerting a pressure normal to its surface to prevent buckling of the yarn during the axial compaction. The compactor 30 shown in FIG. 1(1)) includes a rotary drum 31 and a resilient blanket 32. The drum 31 and the blanket 32 have a width several times the diameter of the yarn 15(0) to permit the yarn to be fed easily through the compactor 30. The blanket 32 is tensioned around press member 33 and guide member 34 and 35. The press member 33 and the guide members 34 and 35 are positioned such that the blanket 32 has a run over a portion of the surface of the drum 31 during its travel and exerts a high pressure normal to the surface of the drum.

The drum 31 is rotatably mounted and is driven by a suitable means not shown. The blanket 32 is driven by the drum 31. The outer surface of the blanket 32 is smooth faced and is accelerated as it passes over the press member 33 and slows down as its curvature changes in passing over the drum 31. The yarn 15(c) is supplied to the compactor unit at the increased velocity of the surface of the blanket 32 as it passes over the press member 33; and the subsequent decrease in surface velocity of the blanket 32 causes a compacting force on a portion of the surface of the yarn 15(0) while providing a normal force against the surface of the yarn to prevent buckling thereof. The compacting force acts on a portion of the circumference of the yarn 15(c) as seen in FIG. 2 to push and crowd the yarn 15(d) axially and thereby shrinks the yarn substantially uniformly throughout. The press member 33 is adjustable toward the drum 31 to create a nip in the blanket 32 as the blanket 32 passes between the pressing member 33 and the drum 31. This nip further increases the velocity of the surface of the blanket 32 entering the nip to cause a corresponding decrease in surface velocity of the blanket surface in the nip to increase the compacting effect on the twisted yarn 15 (c).

The compacted yarn 15(d) passes over a guide roll 40 and is wound on a spool 45. The spool 45 may be a bobbin or other device for use in the subsequent weaving or other use of the twisted paper product. In order to obtain a uniformly wound spool 45 for the subsequent use of the yarn, suitable tensioning means 46 are provided, but such tension as would stretch the yarn back to its original length is avoided. Additionally, I have provided a detection means 47 to detect breaks in the yarn 15(d). The yarn 15(d) then may be dried as desired. The dried compacted yarn has the extensibility, toughness and impact absorbing ability which makes it highly valuable in many fields of use.

Even though the contracting surface of the blanket 32 of the compactor 30 contacts only a portion of the outer surface of the yarn 15(0), I have found that the compaction extends throughout the compacted twisted yarn 15(d). Additionally, on untwisting the compacted yarn 15(d) I have found that the compaction has been provided almost entirely in the ribbon 15 rather than merely shrinking the yarn by telescoping the spirals, and that the direction of maximum extensibility in the longitudinally extending parallel portions of the ribbon 15 is on a bias and at a complementary angle in adjacent parallel portions, as represented by the direction lines shown on the developed portion of the yarn 15(d) in FIG. 3.

In FIG. 4 I have shown a tensile-stretch diagram for the extensibilized twisted yarn of the present invention as compared with ordinary yarn. The curve A represents the tensile-stretch curve for prior twisted yarn made with a paper ribbon having only its natural extensibility. The curve B represents the tensile-stretch curve for the untwisted ribbon forming this prior twisted yarn. The curve C represents the tensile-stretch curve for extensibilized twisted yarn formed in accordance with the present invention; and the curve D represents the tensile-stretch for untwisted extensibilized yarn shown in curve C.

It will be observed from the curves A and C that the tensile-strength of the extensible twisted paper yarn of the present invention is practically the same as the tensile strength of the prior twisted yarn. Also, it will be observed from the curve D that the extensibility or stretch of the untwisted paper ribbon is almost as great as the extensible twisted yarn indicating that the majority of the extensibility imparted by the present process has been added to the ribbon. The measurement of extensibility in the untwisted ribbon was made in the longitudinal direction of the web, since the longitudinally extending parallel portions of the ribbon are too narrow to permit a satisfactory measurement. Therefore, the maximum extensibility of the longitudinally extending parallel portions, which is at a maximum on a bias with the longitudinal direction of the ribbon, is slightly greater in the bias direction than that indicated by curve D.

While I have only shown one embodiment of my invention, it will be obvious to those skilled in the art that other variations and modifications can be made within the teaching of the specification and the scope of the appended claims.

I claim:

1. In a production of an extensible twisted paper product, the sequential steps including rewetting to a moisture content in excess of 15% a previously dry ribbon of paper, folding and twisting said rewet ribbon to define a twisted product, and exerting a pushing and crowding force upon the wet twisted product in a longitudinal direction suflicient to shorten the product at least 2% lengthwise while simultaneously exerting a normal force on said product.

2. A process for producing an extensible twisted paper product, comprising the steps of moistening the ribbon paper to increase its plasticity; folding said moistened ribbon lengthwise to form a plurality of parallel portions; twisting said portions to form tightly wound longitudinally extending spirals; and then compacting the twisted spirals longitudinally thereof while applying a force normal thereto whereby a maximum extensibility is imparted to the paper of which said product is formed in the longitudinal direction of said product.

3. A process for producing an extensible twisted paper product, comprising the steps of moistening a previously dry ribbon of paper to a moisture content in excess of 15%, folding said moistened ribbon lengthwise to form a plurality of parallel portions, twisting said portions about an axis to form said portions into tightly wound longitudinally extending spirals, and then pushing and crowding said twisted portions in the direction of said axis and on a portion of the circumference of said product while simultaneously exerting a normal force on said twisted portions to cause compaction of said portions substantially uniformly throughout to produce an extensibility in said product, said extensibility having a maximum in the direction of said axis.

4. In the production of a yarn from a paper ribbon during which the paper ribbon, while in a moistened condition, is folded and then twisted to form a yarn having longitudinally extending spirals, a method of imparting extensibility to said formed yarn to increase its toughness and flexibility, which method includes confining said formed yarn, While still in a moistened condition, under a normal force to prevent a substantial telescoping of its spirals while simultaneously exerting a lengthwise compressive force on said formed yarn to cause lengthwise shrinkage in the paper of which said yarn is formed.

References Cited in the file of this patent UNITED STATES PATENTS 2,407,926 Hamilton Sept. 17, 1946 2,665,541 Nordstrom Jan. 12, 1954 FOREIGN PATENTS 338,993 Germany July 11, 1921 

